1. Field of the Invention
The present invention relates to a scanning electron microscope and more particularly to a scanning electron microscope for suitably executing positioning to an inspection position on a semiconductor integrated circuit.
2. Discussion of the Background
In correspondence to recent integration of semiconductor devices, a scanning electron microscope is used for observation and inspection of a refined circuit pattern. A scanning electron microscope (hereinafter referred to as CD-SEM) for measuring the size of a specific pattern used on the semiconductor manufacture line is promoted in automation so as to prevent raising of dust by a person in the same way as with other devices or to improve the processing capacity.
In order to automatically measure a target pattern on a wafer, a procedure of moving the observation view field to an approximate position by stage movement, precisely obtaining the measuring pattern position from the observation view field, moving the view field to the position, and measuring the pattern is used. To execute automatic operation, the aforementioned sequence is stored as a file (hereinafter referred to as a recipe file) and at the time of automatic operation, the recipe file is read and the sequence is executed automatically. To detect the precise position of the measuring pattern, the image part (hereinafter referred to as a template) including a characteristic pattern as a guide is registered beforehand and the position is decided by the distance from the pattern position detected by template matching.
In Japanese Patent Application Laid-Open 9-245709, an art for registering a template as a guide beforehand and deciding the target measuring pattern position by matching using the template is disclosed.
A problem as indicated below is imposed in inspection positioning of a sample by the template matching method.
Firstly, to execute template matching, as mentioned above, it is necessary to register a template as a guide beforehand. However, to register a template for template matching, it is necessary to set an environment for introducing and observing a sample such as a semiconductor wafer into a sample chamber. Further, to search for a pattern as a template, a considerable time is required.
In actual positioning by template matching, a normalization correlation value is obtained for the front of an image including a registered pattern and an image to be detected, so that the portion having no information in the template and the noise portion are also calculated. As a result, an incorrect position may be detected due to noise, charge-up of a sample, or uneven contrast.
An object of the present invention is to provide a scanning electron microscope for reducing a process concerning inspection positioning or an input operation, thereby functioning with high precision at high speed.
The present invention, to accomplish the above object, provides a scanning electron microscope having a function for detecting a pattern on the basis of electrons obtained by scanning an electron beam on a sample and identifying a desired position on the basis of the detected pattern and a pattern registered beforehand, which is characterized in that the microscope has a means for setting information concerning the pattern kind, the interval between a plurality of parts constituting the pattern, and the size of parts constituting the pattern and a means for forming a pattern image composed of a plurality of parts on the basis of the information obtained by the concerned means.
By use of such a constitution, a template can be registered without setting an observation environment of a scanning electron microscope such as evacuation. Particularly, with respect to a pattern having a properly regulated arrangement like a line pattern or a hole pattern formed on a semiconductor wafer, if there is information for identifying the size of a plurality of parts forming the pattern and the relative position relationship available, the pattern image can be identified.
The present invention takes up this point, has a constitution of selectively inputting a necessary condition, and forms a pseudo-pattern on the basis of it, so that conventional image forming using an actual pattern image is unnecessary and the operation time can be contracted greatly.
Furthermore, the present invention, to accomplish the above object, provides a scanning electron microscope having a function for detecting a pattern on the basis of electrons obtained by scanning an electron beam on a sample and identifying a desired position on the basis of the detected pattern and a pattern registered beforehand, which is characterized in that the microscope has a means for recognizing the number of detected patterns and/or the interval between a plurality of parts of the detected patterns, a means for calculating the evaluation value on the basis of comparison of the number recognized by the concerned means with the number of registered patterns, and/or a means for calculating, on the basis of comparison of the interval recognized by the means with the interval between the parts of the registered patterns, the evaluation value based on the consistency.
For example, when a pattern composed of a plurality of parts (line patterns or hole patterns) is crushed and the line patterns or the hole patterns are in contact with each other, the pattern is one that length measurement and inspection of the line or hole patterns are not necessary and pattern matching is difficult. According to the present invention, when the number of line patterns and/or the interval are structured so as to evaluate selectively, it can be judged whether each pattern is suitable for length measurement and inspection.